1. Field of Invention
The present invention relates to a fan, and more particularly to a fan of a heat sink.
2. Description of the Related Art
The rapid development of electronic technology has improved the operation speed of the semiconductor devices, such as central processing unit (CPU) or chip. However, operation of the high speed operating semiconductor device generates large amount of heat, which may significantly increase the temperature and may cause abnormal operation of the semiconductor device and also reduce the service life of the semiconductor device if the heat is not timely dissipated.
Accordingly, it is important to dissipate the heat generated by the operation of the semiconductor device for proper operation thereof. Generally, there are two types of heat sinks, namely air cooler and water cooler. The air cooler including a fan is generally employed in electronic devices for dissipating the heat generated during the operation thereof.
The fan is adopted for increasing air circulation to quickly dissipate the heat generated by the operation of semiconductor devices, mostly applied in a personal computer. Manufacturers developed a heat sink with axial air inlet and lateral air outlet suitable for all kinds of environmental conditions of the heating elements of the semiconductor devices.
FIG. 1 shows a DC brushless axial heat sink having axial air inlet and lateral air outlet. The axial heat sink 1 comprises a frame 11, a fan 12 disposed in the frame 11 and a housing 13 covering the fan 12 and the frame 11. The housing 13 comprises an air inlet 131 formed on an upper part of the fan 12 and an air outlet 132 formed on a side of the frame 11.
Referring FIGS. 2 and 3, the fan 12 comprises a hub 121, a plurality of ribs 122 connected to the hub 121, a plurality of blades 123 connected to the plurality of ribs 122 and a ring 124 connected to the blades 123. When the fan 12 rotates due to the operation of the axial heat sink 1, air enters into the top air inlet 131 via the housing 13 as shown in FIG. 3, and the air is then sucked from the top of the hub 121 and exits out via the air outlet of the housing 13 to dissipate the heat.
However, the air sucked via the top air inlet 131 of the housing 13 during the operation of the axial heat sink 1 directly blows and vertically impinges onto the surface of the frame 11 to change the air flow direction, and then exits out via the air outlet 132. Following are some of the defects of the conventional DC brushless heat sink 1 described above.
1. Poor heat dissipation effect: When the axial heat sink 1 operates, the air directly impinges onto the surface of the frame 11, and the air flow direction is drastically changed from axial to lateral direction causing decrease in volume of the incoming air. Thus, not only the passage of air flow is resisted but also the pressure and volume of air exiting out of the heat sink are reduced, and therefore the heat dissipation effect is reduced.
2. Poor air circulation: The ring 124 of the fan 12 is positioned at the outer flange of the blades 123, and therefore when the air vertically impinges on the surface of the frame 11 and then changes the direction to exit out through the gaps of the blades 123, the ring 124 blocks or resists the air from exiting out of the heat sink and thereby reduce the heat dissipation effect.
Therefore, how to overcome the above defects for increasing the volume of air exiting out of the axial heat sink in order to improve the heat dissipation effect is the main object of the present invention.